Archaeologists working in the extreme desert terrain of the Xinjiang Uygur Autonomous Region have moved a step closer to unraveling the mystery of a 40-century-old civilization.

They unearthed 163 tombs containing mummies during their ongoing and long excavation at the mysterious Xiaohe tomb complex.

And it's all thanks to the translation of a diary kept by a Swedish explorer more than 70 years ago.

"We have found more than 30 coffins containing mummies," said Idelisi Abuduresule, head of the Xinjiang Cultural Relics and Archaeology Institute and the excavation team.

The complex is believed to contain 330 or so tombs buried in several layers within a 2,500-square-meter sand dune.

"Most of the items are in the original state of the time when they were buried, and that will help reveal a lot of information about the society and life style of the people of that time," said Idelisi, during his trip back from the desert dust and heat to the autonomous region's capital Urumqi to record the finds, and store the artifacts.

The Xiaohe tombs are believed to have been the burial site of the mysterious Loulan Kingdom, which disappeared without historical trace about 15 centuries ago.

Today's archaeologists are following in the footsteps of Swedish explorer Folke Bergman, who in 1934 ventured south along a river in Lop Nur Desert in the eastern part of Xinjiang.

He said on his return that he'd discovered a dune harboring over 1,000 coffins that date back 4,000 years ago.

He named the place Xiaohe (small river) tombs.

But the river he used to navigate to this ancient site dried up and the dune and its tombs were forgotten about for decades.

In the late 1990s, however, Chinese sociologists translated Bergman's records on archaeological exploration in the area into Chinese and the hunt for dune and its mysteries was once again underway.

In addition to burial articles such as bent wooden blocks and straw baskets, Idelisi's team has found in some coffins wooden figures wrapped in leather instead of mummified bodies.

A bird's-eye view of Xiaohe tombs shows the oval-shape dune taking on the appearance of dumpling pricked full of chopsticks.

Above every coffin protrudes two thick wooden stakes, a symbol some believe of ancient worshiping.

"Considering the scale of the burial site and the mysterious cultural signs, the analyses of the relics are going to yield some exciting results," predicted Idelisi.

The State Administration of Cultural Heritage approved excavation of the Xiaohe tombs in 2003.